We plan to build a circular dichroism spectrometer which will use lasers as light sources. It will have a response time 10,000 times faster with a signal:noise ratio much better than existing instruments, thereby opening a number of new problems to investigation. The major application planned is the measurement of rapid kinetics using stopped-flow techniques. Among the problems to be investigated will be the kinetics and mechanisms of protein and polypeptide folding, cytochrome oxidation and reduction, and catalysis by metal-requiring enzymes. The capability of measuring transient circular dichroism would not only enable us to establish the existence and kinetics of intermediates of biochemical reactions but will enable us to identify their macromolecular conformations. With very few exceptions, it has not been possible to do this by other techniques. The new information would be a start to establishing structure-function relationships for transient biochemical species. Further, because this new information will reflect the detailed mechanisms of intermediate reactions in biological systems, the acquisition of the instrument may indirectly contribute to the discovery of new approaches to regulating these reactions.